Telephone conferences in which several subscribers' telephones are connected via a common pair of wires or to a common connecting point by pairs of wires so that each telephone instrument may be in receipt of transmissions from all the others so as to form a multiparty teleconference connection are well known and many private telephone systems are arranged to be capable of adaptation so as to be able to set up and supervise such multiparty connections under control of the dialling or keysending of the subscribers or on the part of the operator either manually or through the automatic working of the private system in question.
However, through such conference arrangements relying on the control and supervisory arrangements of the private telephone system in question for the establishment and supervision of the teleconferencing connections their scope is commonly limited by the span of the private system so that such dial or key up conference connections can only be made to join subscribers on the same private exchange.
If arrangements are made to extend connections of the conference to subscribers on other exchanges then this is commonly performed through the intervention of the operator. Without the intervention of further distant operators such external connections have to be fanned out individually to each such external conferee from the conference bridge of the originating exchange. Many of these external conferees may be located at or close to the same distant exchange which will result in a multiplicity of paths being set up between the two exchange locations and carrying the same connection resulting in a high connecting charge for the conference, especially if the two exchange locations are far from each other and the connections are made over the public network. This will also result in excessive occupancy on exchange lines to the public network and/or excessive traffic on any privately and/or rented tie lines that are used in such multiple parallel paths.
The principle utility of multiparty conference connections is realised when they span conferee's widely separate locations. Restriction to the environs of the single exchange gives more of a convenience than a service since the accessible conferees are similarly located and least in need of this.